Guide to Chapada Diamantina: Poço Azul

The Poço Azul (blue pool) is a beautiful underground pool that is lit by sunlight from a hole in the cave ceiling and has crystal-clear water that appears bright blue.

Bizarrely, you can also swim in it, though you must take care not to disturb the sediment.

The site of Poço Azul (pr. Poh-so ah-Zool) is a pretty unpreposessing place: just a couple of buildings, a couple of showers, a rack of lifejackets and a gateway surrounding a dusty square.

Change into swimwear, have a shower, fit a life jacket and borrow a mask and snorkel before heading through the gateway and down into the cave with a towel.

The lifejackets are to make sure that you don’t dive down into the water in the cave and cloud the water by disturbing sediment. Take good care in picking out your lifejacket – if it doesn’t fit well, it’ll bunch up around your head as you float upright.

Head down the path and then the wooden steps into the cave and down to the pool. The steps have rubber grips on them, but they are narrow.

With the sun shining through a hole in the roof of the cave, you’ll see the water in the pool below shining bright blue and, if the water’s still, you’ll see how incredibly clear it is. It’s a truly beautiful sight.

The guide down by the pool must have taken thousands of pictures, so does a good job if you want to go in for a swim and have a picture taken.

If you do go in for a swim, you’re asked to get in and out very gently. The best way is to sit at the bottom of the steps and slide in gently in a sitting position.

Paddle around enjoying the water, the clear blue rocks below, the reflections on the ceiling and the amazing light. You can borrow masks and snorkels so that you can make the most of it. If you’re eagle-eyed, you may see some tiny transparent shrimp swimming about.

Dry off and take your kit back up to the surface to shower and change.